Centering device for floating roof



April 16, 1957 J. w. ALLEN CENTERING DEVICE} FOR FLOATING ROOF FiledOct. 5, 1955 INVENTOR. 0km WKZZZeZZ,

United States Patent 2,7ss;91s Dizvicii roe FLOATiisIG noon ronayv.sires, teenage,- 111:, ass n t Gni-al American Trah's'portafionCorporation, Chicago, 11]., a corporation of New York 7 'A ifiietibnOctober 5, 1955, Serial No. 334329 4 Claims. (Cl. 220 26).Thisinyentionrelates to storage tanks andhas for its principal objectthe provision of a new and improved device ofthis kind. V t I,

.1: is am n b t f the inventidn t v de a improved meghani'sm formaintaining a floating roof centank-mw Another object of the inventionis to provide a floating roof centering device which can bemanufactured, installed and maintained in proper working condition at n-4 H. u A

.ns l a ethet, ie.pit e nv t n is 16 P ov de a centering device forafloating roof located solely between t eTedse 9 the r e san e nk W la dh t f epr tected from the weather by the vapor seal forming devices t es. r, Still,anotherobject ofthe inventionis to provide a device forcentering a floating roof in a tank which is of rugged construction andis not deteriorated by corrosion dvt i i e.

Further objects of the invention hot specifically mentionedhere will beapparent from the detailed description andiclaims which follow,reit'ere'nce being had to the acmitpan in w nss n i h a P e r embodimentofthe invention is shown by wayof example and in which: Fig. l, is afragmentary plan view of a tank and roof showing the pusher deviceinstalled therebetween; Fig. 2 is an elevationalview, partly. insection, along theline 2-2 of Fig. 1, looking in the direction of thearrows; J Fig, 3 is'a cross sectional view taken substantially along theline 3;3 of Fig. 1, looking in the direction of the IQW ;.3 d..

Fig. 4 is a view similar to Fig. l, showing a modified qrm o t s uc r.

C -ylindrica l tanks disposed with their axes vertical and equippedyyith roofs which float; upon the surface of liquid stored in the tankare commonly used'for the storage of petroleum products and the like.Such roof "structures are equipped with shoes supported onthe roof anddisposed on the inside surface of shell to form a seal therebetween.Vaporproof membranes are connectto the uppe'r'e'nds'ofthe seal and tothe roof'adja'cent 'it's periplieryto'forhi "a vapem'gntsal between theroof and the ea so that 'evehi'fth'e l qu d stored in'the tank is highlytenths, losses "due to evaporatioh will be minimized.

In such structures the roof is supported upon the surface of the liquidby pontoons, including an outer pontoon extending around the peripheryof the roof. Obviously, for the proper functioning of a device of thiskind, the roof must be maintained centered, or very nearly centered, onthe axis of the tank. Numerous devices have been provided heretofore tomaintain such centering of the roof and the present invention relatesspecifically to such centering devices and provides a new and improveddevice which is inexpensive to install and maintain and is of suchsimple construction as to remain in proper opera- 2,788,913 m fiatent edApr; '16, 1957 tiye condition over a long period of time with a minimumof maintenance. e

In its preferred form, the centering device of the present inventionconsists of arcuate brackets pivotally mounted ,upon the roof in pairsand tensioned to be drawn together, thereby to exert forcesextendingradially outwardly from the roof and against the shoeto maintain thatshoe tightly engaging the inner surface of the tank wall. In theeventthat forces such as prolonged winds in a given direction tend. to move,the roof towards oneside of the tank, the bracketswill be spread apartagainst the tension tending to pull them together, and the force exertedbythe brackets on the shoe and through it on the wallof the tank will beincreased on the side of the roof towards which it has a tendency to.move. On the side of. the tank away from which the roof moves, thebrackets will move towards each other and the force exerted thereby onthe shoe and tank will be decreased to facilitate maintaining the roofcentered.

The centering device of the present invention is located solely betweenthe outer periphery of the roof and the tank wall engaging shoe andbeneath the vapor tight seal therebetween in which position it iscompletely shielded from the weather and not adversely affected by theelemerits. The centering device is located completely between the roofand the shoe and does not extend below the roof or the shoe, andtherefore does not in any way interfere with the travel of the roof upand down in the tank throughout the entire range of movement that theroof is designed to make.

The invention will be best understood by reference to the drawingswherein the outer wall or shell of the tank is shown at 1, the deck ofthe roof at 2, and the outer periphery or rim ofthe roof at 3. As willbe understood by those skilled in the art, floating roofs of this typeare equipped with a boxlike pontoon that extends completely around theperiphery of the roof and provides the necessary buoyancy to the roof.Fitted against the inside surface of the shell 1 is a shoe 4 thatlikewise extends completelyaround the shell and forms a sealthereagainst. The shoes of this type are usually made in sections andequipped with vaportight seals between the sections, thereby enablingthe shoe to maintain a tight contact with the tank ,even though thewalls or shell thereof be slightly out of round. The shoe ,4 issupported .upon the roof of the tank by a plurality of hangers formingno part of the instant invention and therefore omitted from the drawingto avoid 'anunnecessary complication thereof.

Fixed to theupper apart of the shoe 4 and extending therefrom to the.outer periphery of the roof 2 is a flexible vaporproof membrane 5 whichcooperates with the shoe to form a vaportight seal betweenthe roof andtank shell. The details of this seal likewise form no part of thepresentinvention.

The centering device of the present invention consists of a pair ofbracketsltl and 11 pivotally mounted upon ,the vertical outer wall 3 ofthe roof, as indicated at 12.

Eachof the brackets 10 and 11' is generally J-shape'd having anarcuateend remote from the pivot 12 which engages the shoe 4 and exertspressure therea gainst, as will presently appear. The brackets 10 and 11are maintained in a horizontal position by suitable braces 13 fixed tothe brackets and pivotally connected to the wall 3, as indicated at 14.To facilitate ease of installation, the assemblies thus formed aremounted upon bases 15 which can be readily attached to the wall 3 of thetank by welding, riveting or bolting. v

Extending between the brackets 10 and 11 is a flexible tension member16, preferably a chain, at the center of which a weight 17 is hung.Gravity acting upon the weight tends to pull it downwardly, therebyexerting force the tension in the device that aids the movement.

transmitted by the chain 16 to the brackets 10 and 11 and tending torotate them about their pivots toward each other. Thus the brackets 10and 11 are made to exert outwardly extending force on the shoe 4 tomaintain it tightly against the shell 1 and to maintain the roofcentered in the tank. When the roof is centered, the brackets 10 and 11are in a normal position, such as is shown in 'the drawing. It will benoted that as a result of the arcuate shape of the brackets 10 and 11,the distance between the pivots 12 and the pointof engagement of thebracket with the shoe 4 increases as the brackets move towards eachother and decreases as they move apart.

Should forces such as wind acting upon the roof force it oif-center,thus decreasing the distance between the outer wall 3 of the roof andthe tank wall 1, brackets 10 and 11 will thus be rotated away from eachother, chain 16 will be moved upwardly so that the point of attachmentof weight 17 thereto is more nearly in line with the ends of the chain,and as a consequence the force tending to rotate brackets 10 and 11towards each other will thereby be increased, with the result that thepressure exerted on the tank wall by the brackets will be increased tooppose the forces tending to move the roof off-center.

On the side of the tank away from which the forces acting on the rooftend to move the roof, the distance between the outer wall 3 and thetank shell 1 will be increased. Weight 17 will draw the brackets 10 and11 towards each other thereby increasing the angularity of the chain 16,with the result that the component of force placed on the chain by theweight 17 and acting in a horizontal direction will be lessened therebymaking it easier for the diametrically opposed brackets to push the roofback into the center of the tank.

Thus it will be seen that with the centering device of the presentinvention installed on a floating roof, movement of the roof off-centerwill increase the tension in V the'device that opposes such movement andwill decrease As a result, movements of the roof off-center are limitedto small amounts and the roof is thereby maintained centered withsufficient accuracy to permit its proper functioning. V

As will be seen, particularly in Fig. 3, the centering device of thepresent invention is located entirely in the space between the outerwall 3 and the shell and beneath the vapor seal where it is protectedfrom the weather and consequently is not deteriorated thereby. Thecentering device does not project below the roof and shoe, andconsequently in no way interferes with travel of the roof up and down inthe tank throughout the entire range of such travel that the roof isadapted to make.

The tensioning arrangement, consisting of the weight 17 and flexiblemember 16, is advantageous in that it is rugged and forces generated init are dead weight forces which will exist with a minimum interferencefrom corrosion and the like. In certain instances it may be advantageousto tension the brackets and 11 by means of a spring such as 20, Fig. 4.The spring is connected to the brackets by threaded rods 21 and 22 whichprovide for a certain amount of adjustment of the tension of the spring.Obviously, as the brackets are moved away from each other, the spring iselongated and the tension in it thereby increased. As the brackets movetowards each other, the spring is shortened and its tension decreased.

Thus it will be seen that the principle of operation of the modificationshown in Fig. 4 is identical with that hereinbefore described and ,neednot be described in further detail.

The centering device of the present invention being composed of simpleparts can be made rugged economically and when installed upon the tankroof will remain in proper operative condition upon the tank roof willremain in proper operative condition with a minimum of maintenance.Since the centering devices are located beneath the vapor seal, they arenot aifected by weather and are subject only to the efiects of the vaporrising between the roof and shoe, which vapors ordinarily have little orno effect upon the brackets which preferably are composed of iron orsteel. I

While 1 have chosen to show my invention by illustrating and describinga preferred embodiment of it, I have done so by way of example only, asthere are many modifications and adaptations which can be made byoneskilled in the art within the teachings of the invention.

Having thus complied with the statutes and shown and described apreferred embodiment of my invention, what I consider new and desire tohave protected by Letters Patent is pointed out in the appended claims.

What is claimed is:

l. The combination with a vertically disposed cylindrical tank having aroof structure floating upon the surface of liquid therein andcontaining an outer vertically disposed cylindrical wall, and meansincluding 'a shoe supported on and spaced from said roof and engagingthe inner surface of the tank and a flexible membrane extending betweenthe shoe and roof for forming a vaportight sealbetween the tank and roofin all positions of the roof; of means for maintaining the roof centeredin the tank disposed entirely below the seal and between the roof andthe shoe and comprising: a plurality of pairs of rigid lever armsslidably engaging the shoe and pivotally mounted upon the roof forrotation around vertical axes, the pivotal connections of each pair ofarms being closer together than the points of contact of said arms withthe shoe; and means extending between the arms of each pair tensioned torotate the arms toward each other thereby to exert a force outwardly onthe shoe tending to maintain the roof centered in the tank. 7 V

2. Centering means as claimed in claim 1, in which the lever arms arearcuate and are pivotally mounted upon the outer vertical wall of theroof.

3. Centering means as claimed in claim 1, in which the lever arms areconnected together by a flexible member that is tensioned by a weighthung thereon at the middle thereof.

4. Centering means as claimed in claim 1, in which the tensioning meansurging the lever arms together are springs adjustably connected to thelever arm's.

References Cited in the file of this patent UNITED STATES PATENTS GrahamJune. 10, 1952

